The amendment, passed in the Sejm [Polish parliament], also includes plans for extending the deadlines by which developers must secure connection agreements.
It also sets rules to strengthen the Guarantees of Origins scheme — whereby off-takers are given assurances they are sourcing clean electricity.
A final vote on the amendment in the Polish senate is due to be held by the end of July.
The Polish Wind Energy Association believes the 2.5GW onshore wind auction will "probably take place in November or December".
It would follow a 1GW auction for onshore wind, held in November 2018, in which 23 developers secured projects, with low bids of PLN 157.80/MWh (€36/53/MWh).
At the time, industry group WindEurope described the PLN 157.80-216.99/MWh price range as "extremely competitive".
After the Sejm passed the latest amendment to the Renewable Energy Sources Act, WindEurope’s chief policy officer Pierre Tardieu added that new onshore wind projects are now cheaper than new coal and nuclear.
"The Polish government clearly sees an important role for both onshore and offshore wind in meeting their rising energy demand," Tardieu said.
"But the stringent set-back distance law on wind turbines will need fixing to allow for future growth beyond this year’s auction," he added.
Wind farms in Poland must be located at least ten times the height of the turbines from nearby communities, according to current rules.
However, the Polish deputy energy minister has gone on the record saying the government plans to amend the country’s setback rule.